Replacement Gate Sidewall Spacers for Semiconductor Height Control
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Solution Overview
Problem
The existing replacement gate technique in semiconductor device manufacturing faces challenges with the degradation and consumption of insulating material during the pre-clean process, leading to issues such as loss of gate height and variations in gate height across different pitch devices, which can result in processing errors and misalignment.
Innovation Solution
The novel method involves forming reduced-height sidewall spacers that protect the insulating material during the pre-clean process, using a layer of insulating material with better etch selectivity and forming secondary sidewall spacers to define the gate cavity, thereby preventing excessive consumption of the insulating material and maintaining consistent gate structure height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pre-clean process is performed to remove contaminants, then cleaning effectiveness is improved, but insulating material degradation increases
Solution Approach 1:
A sacrificial spacer layer is introduced as an intermediary protective barrier between the insulating material and the harsh pre-clean chemistry. The spacer layer absorbs the chemical attack during pre-clean, preventing direct contact with the insulating material, and is later removed to reveal the protected insulating material underneath.
Solution Approach 2:
The sacrificial spacer layer is formed beforehand to provide protection before the pre-clean process occurs. This preliminary protective action ensures that the insulating material is shielded during the cleaning process, and the spacer is subsequently removed after it has served its protective purpose.
2Loss of substance
If the insulating material layer is made thicker to prevent degradation, then material protection is improved, but gate height consistency deteriorates
Solution Approach 1:
The sacrificial spacer acts as a temporary intermediary that provides protection without becoming part of the final gate structure. It allows sufficient material thickness for protection while maintaining precise gate height control, as the spacer is removed after serving its protective function.
Solution Approach 2:
The sacrificial spacer is a temporary, disposable structure formed specifically for protection during processing. It is intentionally designed to be consumed or removed after its protective purpose is fulfilled, allowing optimal thickness without compromising final device dimensions.
3Loss of substance
If the insulating material has better etch selectivity, then material preservation is improved, but pre-clean effectiveness deteriorates
Solution Approach 1:
The sacrificial spacer serves as a mediator that has high etch selectivity to the pre-clean chemistry, allowing effective cleaning while the insulating material remains protected. The spacer is designed to be selectively removed while preserving the insulating material underneath.
Solution Approach 2:
Different regions have different etch selectivity requirements: the sacrificial spacer has high selectivity to enable effective pre-clean, while the insulating material has appropriate selectivity for gate formation. Each material is optimized for its specific function in the process sequence.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces the degradation of insulating material, maintains consistent gate height across devices with varying pitches, and enhances the reliability of subsequent processing steps by ensuring proper electrical isolation and contact formation.
Implementation Method 1
performing at least one etching process to remove the gate cap layer and a portion of the first sidewall spacers
Data Source
AI summary
One method includes forming first sidewall spacers adjacent opposite sides of a sacrificial gate structure and a gate cap layer, removing the gate cap layer and a portion of the first sidewall spacers to define reduced-height first sidewall spacers, forming second sidewall spacers, removing the sacrificial gate structure to thereby define a gate cavity, whereby a portion of the gate cavity is laterally defined by the second sidewall spacers, and forming a replacement gate structure in the gate cavity, wherein at least a first portion of the replacement gate structure is positioned between the second sidewall spacers. A device includes a gate structure positioned above the substrate between first and second spaced-apart portions of a layer of insulating material and a plurality of first sidewall spacers, each of which are positioned between the gate structure and on one of the first and second portions of the layer of insulating material.